scholarly journals Effects of the colour of photophase light on locomotor activity in a nocturnal and a diurnal South African rodent

2019 ◽  
Vol 15 (10) ◽  
pp. 20190597 ◽  
Author(s):  
Ingrid van der Merwe ◽  
Nigel C. Bennett ◽  
Abraham Haim ◽  
Maria K. Oosthuizen
Keyword(s):  
Locomotor Activity ◽  
South African ◽  
Temporal Organization ◽  
Dark Cycle ◽  
Long Wavelength ◽  
Rhabdomys Pumilio ◽  
Nocturnal Species ◽  
Wavelength Light ◽  
Diurnal Species ◽  
Effect Of Light

Many physiological and behavioural responses to varying qualities of light, particularly during the night (scotophase), have been well documented in rodents. We used varying wavelengths of day-time (photophase) lighting to assess daily responses in locomotor activity in the nocturnal Namaqua rock mouse ( Micaelamys namaquensis ) and diurnal four-striped field mouse ( Rhabdomys pumilio ). Animals were exposed to three light–dark cycle regimes: a short-wavelength- (SWLC, blue), a medium-wavelength- (MWLC, green) and a long-wavelength light–dark cycle (LWLC, red). Overall, daily locomotor activity of both species changed according to different wavelengths of light: the diurnal species displayed most activity under the SWLC and the nocturnal species exhibited the highest levels of activity under the LWLC. Both species showed an increase in diurnal activity and a decrease in nocturnal activity under the LWLC. These results indicate an attenuated responsiveness to long-wavelength light in the nocturnal species, but this does not appear to be true for the diurnal species. These results emphasize that the effect of light on the locomotor activity of animals depends on both the properties of the light and the temporal organization of activity of a species.

Daily hypothermia and torpor in a tropical primate: synchronization by 24-h light-dark cycle

2001 ◽  
Vol 281 (6) ◽  
pp. R1925-R1933 ◽  
Author(s):  
M. Perret ◽  
F. Aujard
Keyword(s):  
Locomotor Activity ◽  
Fixed Time ◽  
Temporal Organization ◽  
Physiological Changes ◽  
Dark Cycle ◽  
Subjective Night ◽  
Free Running ◽  
Rapid Drop ◽  
Gray Mouse Lemur ◽  
Short Days

To study the temporal organization of daily hypothermia and torpor in a nocturnal Malagasy primate, the gray mouse lemur, body temperature (Tb) and locomotor activity were recorded using telemetry on 39 males held in 24-h light-dark cycles of different photoperiods. Under free-running condition, the circadian Tb and locomotor activity rhythms had a period shorter than 24 h. Circadian daily hypothermia started by a rapid drop in Tb (0.24°C/10 min) at the end of subjective night (13 h 25 ± 20 min) and was characterized by minimal Tb values 3 h 20 ± 5 min later. Spontaneous arousal from daily hypothermia occurred at a fixed time (6 h 05 ± 15 min, n = 7) after the beginning of subjective day. In animals exposed to 24-h light-dark cycles with night duration varying from 10 to 14 h, locomotor activity was strictly restricted to dark time, but the temporal organization of daily hypothermia was not modified, although changes in amplitude of Tb rhythm were observed. Daily hypothermia was directly induced by light and lasted 5 h 10 ± 10 min, with minimal Tb values 3 h 30 ± 30 min ( n = 28) after lights on, on condition that nighttime did not exceed the duration of subjective night. However, in animals exposed to 24-h light-dark cycles with night duration varying from 10 to 5 h, the limit of induction of daily hypothermia by light was ∼9 h after the beginning of night. Finally, under short days (14:10-h light-dark cycle), long bouts (6 h 50 ± 40 min) of actual torpor (minimum Tb 27.6 ± 0.9°C) were observed and would involve mechanisms depending on physiological changes induced by short day exposure.

scholarly journals Selected Scattering on Quasi-Ordered Hexagonal Close-Packed Al Nanodents for Tunable Output of White LEDs

2019 ◽  
Vol 9 (17) ◽  
pp. 3626
Author(s):  
Junfeng Zhao ◽  
Xinxiang Yu ◽  
Zhiguo Zhao ◽  
Xiaoyan Dong ◽  
Dandan Shi ◽  
...  
Keyword(s):  
Near Field ◽  
Light Emitting ◽  
White Leds ◽  
Long Wavelength ◽  
Hexagonal Close Packed ◽  
Light Coupling ◽  
Short Wavelength Light ◽  
White Light Emitting Diodes ◽  
Wavelength Light ◽  
Effect Of Light

Quasi-ordered hexagonal close-packed Al nanodents, with depths of 30 nm and top-diameters of 300 nm prepared by electrochemical anodizing, are used to manage the output spectrum of white Light Emitting Diodes (LEDs). Significant short wavelength light, with a peak of 450 nm, displays significant scattering enhancements on these Al nanodents with the increment of the angle of the incidence, while long wavelength light, with a peak of 550 nm, shows weaker scattering on Al nanodents with the increment of theincidence angle. Near-field and far-field simulations reveal the effect of light coupling in the holes of Al nanodents on the selected scattering. This work could provide a striking new way to make use of cheap white LEDs.

scholarly journals Demonstration of epitaxial growth of strain-relaxed GaN films on graphene/SiC substrates for long wavelength light-emitting diodes

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Ye Yu ◽  
Tao Wang ◽  
Xiufang Chen ◽  
Lidong Zhang ◽  
Yang Wang ◽  
...  
Keyword(s):  
Epitaxial Growth ◽  
Light Emitting Diodes ◽  
Nitrogen Plasma ◽  
Biaxial Stress ◽  
Organic Chemical ◽  
Graphene Surface ◽  
Light Emitting ◽  
Long Wavelength ◽  
Pre Treatment ◽  
Wavelength Light

AbstractStrain modulation is crucial for heteroepitaxy such as GaN on foreign substrates. Here, the epitaxy of strain-relaxed GaN films on graphene/SiC substrates by metal-organic chemical vapor deposition is demonstrated. Graphene was directly prepared on SiC substrates by thermal decomposition. Its pre-treatment with nitrogen-plasma can introduce C–N dangling bonds, which provides nucleation sites for subsequent epitaxial growth. The scanning transmission electron microscopy measurements confirm that part of graphene surface was etched by nitrogen-plasma. We study the growth behavior on different areas of graphene surface after pre-treatment, and propose a growth model to explain the epitaxial growth mechanism of GaN films on graphene. Significantly, graphene is found to be effective to reduce the biaxial stress in GaN films and the strain relaxation improves indium-atom incorporation in InGaN/GaN multiple quantum wells (MQWs) active region, which results in the obvious red-shift of light-emitting wavelength of InGaN/GaN MQWs. This work opens up a new way for the fabrication of GaN-based long wavelength light-emitting diodes.

scholarly journals Effects of photoperiod on daily locomotor activity, energy expenditure, and feeding behavior in a seasonal mammal

2010 ◽  
Vol 298 (5) ◽  
pp. R1409-R1416 ◽  
Author(s):  
Amy Warner ◽  
Preeti H. Jethwa ◽  
Catherine A. Wyse ◽  
Helen I'Anson ◽  
John M. Brameld ◽  
...  
Keyword(s):  
Body Weight ◽  
Locomotor Activity ◽  
Energy Expenditure ◽  
Feeding Behavior ◽  
Heat Production ◽  
Prolonged Exposure ◽  
Dark Phase ◽  
Daily Rhythms ◽  
Dark Cycle ◽  
Activity Energy

The objective of this study was to determine whether the previously observed effects of photoperiod on body weight in Siberian hamsters were due to changes in the daily patterns of locomotor activity, energy expenditure, and/or feeding behavior. Adult males were monitored through a seasonal cycle using an automated comprehensive laboratory animal monitoring system (CLAMS). Exposure to a short-day photoperiod (SD; 8:16-h light-dark cycle) induced a significant decline in body weight, and oxygen consumption (V̇o2), carbon dioxide production (V̇co2), and heat production all decreased reaching a nadir by 16 wk of SD. Clear daily rhythms in locomotor activity, V̇o2, and V̇co2 were observed at the start of the study, but these all progressively diminished after prolonged exposure to SD. Rhythms in feeding behavior were also detected initially, reflecting an increase in meal frequency but not duration during the dark phase. This rhythm was lost by 8 wk of SD exposure such that food intake was relatively constant across dark and light phases. After 18 wk in SD, hamsters were transferred to a long-day photoperiod (LD; 16:8-h light-dark cycle), which induced significant weight gain. This was associated with an increase in energy intake within 2 wk, while V̇o2, V̇co2, and heat production all increased back to basal levels. Rhythmicity was reestablished within 4 wk of reexposure to long days. These results demonstrate that photoperiod impacts on body weight via complex changes in locomotor activity, energy expenditure, and feeding behavior, with a striking loss of daily rhythms during SD exposure.

scholarly journals Drugs of Abuse Can Entrain Circadian Rhythms

2007 ◽  
Vol 7 ◽  
pp. 203-212 ◽  
Author(s):  
Ann E. K. Kosobud ◽  
Andrea G. Gillman ◽  
Joseph K. Leffel ◽  
Norman C. Pecoraro ◽  
G. V. Rebec ◽  
...  
Keyword(s):  
Locomotor Activity ◽  
Circadian Rhythms ◽  
Drug Metabolism ◽  
Suprachiasmatic Nucleus ◽  
Drugs Of Abuse ◽  
Social Cues ◽  
Dark Cycle ◽  
Drug Reward ◽  
Locomotor Stimulation ◽  
Almost All

Circadian rhythms prepare organisms for predictable events during the Earth's 24-h day. These rhythms are entrained by a variety of stimuli. Light is the most ubiquitous and best known zeitgeber, but a number of others have been identified, including food, social cues, locomotor activity, and, most recently drugs of abuse. Given the diversity of zeitgebers, it is probably not surprising that genes capable of clock functions are located throughout almost all organs and tissues. Recent evidence suggests that drugs of abuse can directly entrain some circadian rhythms. We have report here that entrainment by drugs of abuse is independent of the suprachiasmatic nucleus and the light/dark cycle, is not dependent on direct locomotor stimulation, and is shared by a variety of classes of drugs of abuse. We suggest that drug-entrained rhythms reflect variations in underlying neurophysiological states. This could be the basis for known daily variations in drug metabolism, tolerance, and sensitivity to drug reward. These rhythms could also take the form of daily periods of increased motivation to seek and take drugs, and thus contribute to abuse, addiction and relapse.

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